Electric lamp



Y M h 10, 1942. KERN 2,275,768

a ELECTRIC LAMP Filed Nov. 12, 1940 lnven'tors Josef Kern rman Kref'ft,

he'n' Attorneg.

Patented Mar. 10, 1942 ELECTRIC LAMP Josef Kern and Herman Krefi't,Berlin-Schoneberg, Germany, assignors to General Electric Company, acorporation of New York Application November 12, 1940, Serial No.

In Germany June 17,- 1939 4 Claims.-

The present invention relates to electric lamps generally and moreparticularly the invention relates to such lamps comprising anincandescent filament and a gaseous electric discharge device capable ofoperation on alternating current with a vapor pressure in the order ofatmospheres.

Lamps of the above type are now known in the art which operate directlyon commercial voltages and can be mounted in sockets used" forincandescent lamps without .extemal auxiliary apparatus. The practice inthe art heretofore has been to operate the discharge device at a vaporpressure of about 1 to 8 atmospheres in series with an incandescentfilament of such size that the main part of the line voltage isdissipated in the seriesfilament. This proportioning mospheres, aspecific power consumption of morethan 200 watts, preferably more than300 watts,

per centimeter of arc length and a specific wallload of more than ,20watts per square centimeter of the inner surface of the container. Weprefer to mount the discharge lamp in a vitreous, bulb provided with ascrew base and'to connect in series therewith an' incandesciblefilament, also mounted in the bulb, said filament between the voltagedissipated by the filament and that dissipated by the discharge is madenecessary by the fact that the high pressure discharge device has a highreignition peak occurring in each half cycle of the alternating currentand the fact that commercial current sources have unavoidable voltagefluctuations. twice the voltage occurring at the electrodes is necessaryfor insuring reignition of the arc.-

The object of the present invention is to provide an electric lamp ofthe above type which Thus having a resistance value such that during theoperation of the lamp the voltage drop across thefilament'is less than45 per cent of the line voltage.

In the drawing accompanying and forming part of this specification anembodiment of the invention is shown in a front elevation, partlysectional view.

Referring to the drawing the electric lamp comprises a bulb 2 ofvitreous materiaLsuch as glass, having a metal screw base I attachedthereto and containing a high pressure metal vapor discharge lamp, anincandescible filament and current leads for said dischargelamp and hasa greater light output than those now known in the art. Another objectof the invention is to provide a gaseous electric discharge lamp of thehigh vapor pressure type capable of operation on alternating currentandwhich has a lower reignition voltage on each half cycle of thealternating current than those now known in the art.

Still further objects and advantages of the invention will be apparentto those skilled in the art from the following detailed descriptionthere of and from the appended claims.

We have discovered that the reignition voltage of discharge lamps of theabove type decreases with increasing current and voltage gradient. thatis, with increasing energy consumption per unit length of the arc path.We have utilized our discovery to provide a new the above type.

The new lamp comprises a discharge device having a vitreous container ofhigh softening point material, such as quartz, providing a spherical orkeg shaped discharge chamber of 15 mm. or less insidediameter and havingcooperating thermionic electrodes sealed therein. Said electrodes areseparated a distance less than 5 mm. The discharge lamp is capable ofoperation with a vapor pressure greater than 25 atkind of lamp of saidfilament. The discharge lamp has a'container 3 of vitreous materialhaving a high softening point, such as 'quartz, providing a sphericaldischarge chamber of about 8 mm. inside diameter. Two cooperatingelectrodes 5 separated a distance of about 3 mm. are sealed into saidcon tainer 3. Part of the current leads for said elec-. trodes 5 areimbedded in the stems of the con-r tainer 3 and comprise metal foil,such as molyb J denum foil,'as is well known in this art. Said pressureof about atmospheres.

electrodes 5 preferably consist of small, perfo-' rated tungsten shells,cone shaped in the direc- I tion of the discharge path and containingthorium oxide or zirconium oxide. Other types of activated electrodesknown in the art, such as wire helices surrounding or impregnated withactivating materials, are used when desired.

, Said container 3 has therein a rare gas, such as argon, at a pressureof about 20 mm. When rapid heating of the device is desired to shortenthe time required to attain operating equilibrium after starting thepressure of the gas is increased; A gas pressure of about 400 mm. iseffective for this purpose though pressures lowerathan this are usefulfor the same purpose. A body of mercury 6 is present in-said container,in such amount that when the device is at operating equilibrium thevapor atmo'sphere is unsaturated, and has a The are voltage increaseswith a rising vapor pressure to about volts and the voltage drop acrossthe filament 6 decreases to about 75 volts. Thus the ment and a gaseouselectric discharge device mounted in said bulb, said filament beingconnected in series with said discharge device and of the dischargedevice is higher than that of the incandescent filament.

When the arc current is one-half ampere thewattage input is about 72.5watts which is a specific wall load of about 36 'watts per squarecentimeter of the inner surface of the container 3 and a specific powerconsumption of about 250 watts per centimeter of the length of the arcpath.

The bulb 2 contains an inert gaseous atmosphere, such as a mixture ofargon and nitrogen. When glare is to be avoided a light diffusing bulb 2is preferred. When the considerable ultra violet light output of thedischarge device is desired for utilization external to the lamp thebulb 2 is made of a vitreous material capable of transmitting suchradiation. When the lamp is used for purposes of illumination we preferto coat the inner surface of the bulb 2 with luminescent powder 1 or tomake the bulb 2 of a luminescent glass.

When desired another series resistance of the type which automaticallydecreases in value during the starting period is mounted in the bulb 2or in the base I to prevent excessive currents inthe lamp when potentialis first applied thereto. It will be understood, of course, that whereprior devices for lowering the reignition voltage, such as auxiliaryelectrodes or electrically conducting strips, are used in the new lamp,the operating.

voltage of the discharge device can be increased still further.

1 While we have pointed out in the annexed claim certain novel featuresof the invention, it will be understood, of course, thatvariousmodifications and changes in theform and details of the lamp describedabove and illustrated in the drawing may be made by those skilled in theart without departure from the spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An electric lamp capable of operating, on

alternating current and comprising in combination a sealed bulb ofvitreous material, gaseous electric discharge device and ohmicresistance means mounted in said bulb said means being connected inseries with said device and constituting the sole ballast meanstherefor, said discharge device having a vitreous container providing aspherical discharge chamber which is 'not more than mm. in diameter, apair of constituting the sole ballast means therefor, said dischargedevice having an ultraviolet ray transmitting vitreous containerproviding aspherical discharge chamber which is not more than 15 mm. indiameter, a pair of spaced, cooperating electrodes sealed into saidcontainer and sepa rated a distance of less than 5 mm. from each other,a starting gas and a quantity of mercury in said container, saiddischarge device being capable of operating with a vapor pressure of atleast 25 atmospheres, a specific current load of more than "200 wattsper centimeter of length of the arc 'path and a specific wall load ofmore than 20 watts per square centimeter of the inner surface of thecontainer, the operating voltage of said device being more than 55 percent of the voltage applied across the terminals of said lamp when saiddevice is at operating equilibrium. l

3. An electric lamp capable of operating on alternating current andcomprising in combination a sealed bulb of vitreous material,anincandescible filament and a gaseous electric discharge device mountedin said bulb, said filament being connected in series with'saiddischarge device and constituting the sole ballast means therefor, saiddischarge device having an ultraviolet ray transmitting vitreouscontainer providing a spherical discharge chamber which is not more than15 mm. in diameter, a pair of spaced, cooperating electrodes sealed intosaid container and separated a distance of less than 5 mm. from eachother, a starting gas and a quantity of mercury in said container, saiddischarge device being capable of operating with a vapor pressure of atleast25 atmospheres, a specific current load of more than 200 watts percentimeter of length of the arc path and a specific wall load of morethan 20 watts per square centimeter of the inner surface of thecontainer, the operating voltage drop across said filament b'eing morethan per cent of the voltage applied across the terminals of said lampwhen said device is at operating equilibrium and luminescent materialsupported by said bulb.

4. An electric lamp unit comprising in combination, anohmic ballastresistance means and a gaseous electric discharge lamp device con-'nected in series therewith, said resistance means constituting the soleballast for said device said discharge device having a vitreouscontainer providing a spherical discharge chamber not more than 15 mm.in diameter, spaced, cooperating electrodes sealed into said containerand separated a distance of less than 5 mm., a starting gas and aquantity of vaporizable metal in said container, said discharge devicebeing capable of operating with a vapor pressure of at least 25atspecific wall load of more than 20watts per square centimeter of theinner surface of the container, the operating voltage of said devicemitting vitreous material, an incandescible filamospheres, a specificcurrent load of more than 200 watts per centimeter of length of the arcpath and a specific wall load of more than 20 watts per squarecentimeter of the inner surface of the container, the reignition voltageof said discharge device being so low that the device is successfullyoperated even when the operating voltage thereof: is more than 55 percent of the voltage applied to said lamp unit when said vdevice is atoperating equilibrium.

JOSEF KERN. HERMANN KREFFT.

CERTIFICATE or comcmon. i 3 Patent No. 2,27 ,768. a n 10, 1911.2.

JosEF KERN, ET AL It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows: Page 2, 590-. 0nd column, line 14.5, claim 5, for "dropacross said filament" read of said device--; and that the said LettersPatent should be read with this correction therein that the same mayconform to the record of the case in the Patent Office.

Signed and sealed thie 20th day of October, A. 1)., 191 .2.

Henry Van Arsda le, (Seal) Acting Commissioner of Patents.

